2.

Dental (Tooth) Anatomy

v
Terminology

n
Groups of Teeth

Teeth, as they exist in the mouth, can be placed into any
of three broad groupings, the maxillary or mandibular, right or left, anteriors
or posteriors. These groupings apply to both the natural dentition and to
artificial teeth:

¨ Maxillary or Mandibular

A person has two jaws, a maxillary (upper) and a mandibular
(lower). The teeth in these jaws are called either maxillary or
mandibular teeth. The combination of natural teeth and supporting alveolar
bone that is found in an upper or a lower jaw is called a dental arch
. When natural teeth are extracted, the healed alveolar process is called
the residual ridge. Artificial teeth sit over residual ridges so they
coincide with the original arch form.

¨ Right or Left

If we split the two dental arches down the midline from
front to back, the arches can be divided into upper and lower right sections
and upper and lower left sections. Since one of these sections represents
one-fourth of the upper and lower arches taken together, the section is called
a quadrant (Figure 2-1). If a tooth is located to the left of the midline
in the upper arch, the tooth is part of the maxillary left quadrant (etc.).

¨ Anteriors or Posteriors
(Figure 2-2)

Teeth can also be classified as anteriors (incisors and
cuspids) or posteriors (bicuspids and molars). A complete adult natural dentition
has 32 teeth; each arch contains 16. The teeth in an arch are composed of
6 anteriors (cuspid to cuspid) and 10 posteriors (all teeth distal to the
cuspids). There are 3 anteriors and 5 posteriors in a quadrant.

Figure 2-1. Mandibular Right Quadrant

Anterior
Posterior Teeth

Figure 2-2. Anterior
and Posterior Teeth

NOTE: Complete dentures for the upper and lower arches usually consist
of 28 teeth. The 4 third molars are not used.

n
Names of Teeth (Figure 2-3)

¨ Anteriors

Central
and Lateral Incisors. In each quadrant, the two teeth nearest
the midline of the dental arches are called incisors. The first
incisor on either side of the midline is called a central incisor.
The second incisor from the midline of either arch is called a lateral
incisor. The word incisor describes their functions of incising or
cutting food.

Cuspids
. A cuspid is so named because its cutting edge is a single, pointed elevation
or cusp. Cuspids are sometimes called canines. They are
used to tear food. Each dental arch has two cuspids.

¨ Posteriors

Biscuspids. Biscupids are so named because most have two
cusps on their chewing surfaces. They are also called premolars
because they occupy an anatomical position mesial to the molars.
There are eight biscupids, two in each quadrant, functioning as
seizing and grinding teeth.

The two biscupids in any given quadrant are
further called first and second
biscupids,
the first being located
immediately
behind the cuspid.

Molars. molars, the largest teeth in
the dental arches, lie directly behind the bicuspids and funstion as
grinders during mastication (chewing). under normal conditions, there
are six molars in each arch (three in each quadrant). They are called
first, second, and third molars, the first molarbeing the
first tooth distal to the second bicuspid.

n
Number Substitutes for Names of Teeth (Figure 2-4)

Formal descriptions like "maxillary right molar" and "mandibular
left lateral incisor" can be time- consuming when many people must be
examined in a short time, and too lengthy when space on forms is limited.
Dentists often use numerical shorthand as a substitute for complete, formal
tooth names. The full complement of natural teeth is numbered #1 through
#32. Numbers 1 through #16 are in the maxillary arch; the upper right third
molar is #1, the upper right second molar is #2, and as you proceed in
consecutive order around the maxillary arch to the upper left third molar,
you end with #16. Numbers 17 through #32 are in the mandibular arch; the
lower left third molar is #17, the lower left second molar is #18, and
as you proceed around the mandibular arch to the lower right third molar
you end with #32.

Figure 2-4. Number Substitutes for Names of Teeth

1.
Right maxillary third molar.

2.
Right maxillary second molar.

3.
Right maxillary first molar.

4.
Right maxillary second bicuspid.

5.
Right maxillary first bicuspid.

6.
Right maxillary cuspid

7.
Right maxillary lateral incisor.

8.
Right maxillary central incisor.

9.
Left maxillary central incisor.

10.
Left maxillary lateral incisor.

11.
Left maxillary cuspid.

12.
Left maxillary first bicuspid.

13.
Left maxillary second bicuspid.

14.
Left maxillary first molar.

15.
Left maxillary second molar.

16.
Left maxillary third molar.

17.
Left mandibular third molar.

18.
Left mandibular second molar.

19.
Left mandibular first molar.

20.
Left mandibular second bicuspid.

21.
Left mandibular first bicuspid.

22.
Left mandibular cuspid.

23.
Left mandibular lateral incisor.

24.
Left mandibular central incisor.

25.
Right mandibular central incisor.

26.
Right mandibu!ar lateral incisor.

27.
Right mandibular cuspid.

28.
Right mandibular first bicuspid.

29.
Right mandibular second bicuspid.

30.
Right mandibular first molar.

31.
Right mandibular second molar.

32.
Right mandibular third molar.

n
Structure of the Teeth and Supporting Tissues (Figure 2-5)

¨ Teeth

A tooth is divided into two parts, the
crown and the root. The anatomical crown isthe
part of the tooth covered with enamel. The root of a tooth is embedded in
alveolar bone and covered with cementum.

NOTE: In young
people, areas of the anatomical crown are frequently buried in gingival tissue.
As a person gets older it becomes common for a tooth’s enamel to be completely
exposed above the gingiva and to have root surface showing. The term clinical
crown is applied to the part of the tooth that is visible above the gingiva
to include root surface.

The bulk of a tooth is composed of a bone-like
substance called dentin which is covered by enamel to form the crown
and cementum to form the root. The line of division between the crown
and root is called the cervical line or cemento enamel junction. The
dividing line is found in a somewhat constricted region on the tooth’s surface
called the cervix or neck. The tip of the root is known as the apex.

The tooth contains an aggregate of blood
vessels, nerves, and cellular connective tissue called the dental pulp.
The dental pulp is housed within a pulp chamber and root canal of a tooth.
Anterior teeth ordinarily have one root canal; multiple canals occur in posterior
teeth. The nerves and blood vessels enter and leave the tooth through an
opening called the apical foramen at or near the apex of the root.

¨
Supporting Structures of the Teeth

The supporting tissues of the teeth are
collectively called the periodontium. The periodontium consists of
the alveolar process of the maxillae and the mandible, the periodontal ligament,
the cementum of the tooth, and the gingiva.

Alveolar
Process. The alveolar process is the portion of the
maxillae or mandible in which the roots of the teeth are embedded and
by which tooth roots are supported. An alveolar process consists of three
kinds of bone. They are the outer cortical plate, lamina dura, and spongy
bone. The outer cortical plate is a compact layer of bone on the
bone’s surface. The lamina dura is a thin, dense layer
of bone that lines tooth sockets. The lamina aura is a specialized continuation
of the cortical plate. Spongy bone is the less dense, cancellous
bone representing the alveolar process’ central mass.

Periodontal
Ligament. The periodontal ligament is a thin, fibrous
ligament connecting a tooth to the lamina aura of the bony socket. Normally,
teeth do not contact the bone directly; a tooth is suspended in its socket
by the fibers of the ligament. This arrangement allows each tooth limited
individual movement. The fibers act as shock absorbers to cushion the
force of chewing impacts.

Cementum. The cementum is the only tissue considered
as both a basic part of the tooth and a component of the periodontium.
It is a thin, calcified layer of tissue that completely covers the dentin
of a tooth’s root. Cementum is formed during the development of the root.
It functions as an area of attachment for periodontal ligament fibers.

Gingiva
(Figure 2-6). The gingiva is the specialized
mucous membrane covering the alveolar processes and encircling the necks
of the teeth. It aids in the support of the teeth, and protects the alveolar
process and periodontal ligament from bacterial invasion. Healthy gingiva
is pale pink, firm, and resilient. It is divided into two types, free and attached
gingiva.

Free gingiva is "free" to the extent that it can be displaced; it
is not tightly bound to anything underneath it. Free gingiva extends
from the gingival crest to the bottom of the gingival sulcus. At the
bottom of the sulcus, an epithelial attachment joins the free
gingiva to the tooth surface. The interdental papilla is the
portion of the free gingiva that fills the proximal space below the contact
areas of adjacent teeth. It helps prevent food from packing between the
teeth.

Attached
gingiva covers the labial cortical plate of the alveolar process.
It is firmly fixed to underlying bone.

n Crown Morphology (Contours)

As you study anatomy, you will discover
there are almost no perfectly flat or perfectly straight surfaces; most
surfaces are curved. The contour of a crown is a combination of convex
and concave curves. A convex surface is one which is curved outward;
a concave is curved inward.

¨
Tooth Surfaces (Figure 2-7)

Proximal. A tooth has two proximal surfaces, one that is oriented
toward the midline of the dental arch and another that is oriented away
from the midline of the arch.

- Mesial. The mesial is the
proximal surface closest to the midline of the arch.

- Distal
.
The distal is the proximal surface oriented away from the midline
of the arch.

Facial. The facial is the surface of a tooth that "faces"
toward the lips or cheeks. When there is a requirement to be more specific,
terms like labial and buccal are used:

- Labial
.
The labial is the surface of an anterior tooth that faces toward
the lips.

- Buccal.
The buccal is the surface of a posterior tooth that faces toward the
cheek.

Lingual
.The surface of a tooth facing toward the tongue is called the lingual.

Incisal. The cutting edge of an anterior tooth.

Occlusal. The chewing surface of a posterior tooth.

Figure 2-7. Tooth Surface

Figure 2-9. Anterior and Posterior Crown Divisions

Figure 2-8. Long Axis

Long Axis and Axial Surface
(Figure 2-8). The long axis of a tooth is an imaginary line that goes
through the crown and root around which the substance of a tooth is most
symmetrically distributed. Any surface of a tooth that is parallel to
the long axis is called an axial surface (for example, mesial, distal,
facial, or lingual surfaces).

Division of a Crown Into Thirds
(Figure 2-9). The facial, lingual, mesial, and distal surfaces of a crown
can be divided into thirds, both horizontally and longitudinally:

Horizontal Division.
Each axial surface of a crown is divided horizontally into a cervical,
a middle, and an occlusal (or incisal) third.

Longitudinal Division.
Each mesial or distal axial surface may be divided into a facial, a middle,
and a lingual third; each facial or lingual surface may be divided into
a mesial, a middle, and a distal third.

Line Angle. An
angle formed by the junction of two crown surfaces. It derives its name
from those surfaces. There are eight line angles per tooth:

-
Anterior Tooth Line Angles

1. Mesiolabial

2. Mesiolingual

3. Distolabial

4. Distolingual

5. Labioincisal

6. Linguoincisal

7. Mesioincisal

8. Distoincisal

-
Posterior Tooth Line Angles

1. Mesiobuccal

2. Mesiolingual

3. Distobuccal

4. Distolingual

5. Bucco occlusal

6. Linguo occlusal

7. Disto occlusal

8. Mesio occlusal

Point Angle

. A point angle is formed by the junction
of three crown surfaces; the name of the point angle is derived by
combining the names of the three surfaces.

- Anterior Tooth Point Angles

1. Mesiolabioincisal

2. Mesiolinguoincisal

3. Distolabioincisal

4. Distolinguoincisal

- Posterior Tooth Point Angles

1. Mesiobucco-occlusal

2. Mesiolinguo-occlusal

3. Distobucco-occlusal

4. Distolinguo-occlusal

¨ Distinctive Crown Convexities
and Concavities

Convexities

Lobe (Figure 2-10) . A lobe is one of
the primary anatomical divisions of a crown; all teeth develop from either
four or five lobes (for example, a central incisor forms from four lobes
while first molars develop from five lobes.) Lobes are usually separated
by readily identifiable developmental grooves.

Cingulum (Figure 2-12). A cingulum is found on the lingual aspect
of an anterior tooth. It is a convex mount of enamel localized to the
cervical one-third of the crown.

Figure 2-11. Mamelons

Figure 2-12.
Cingulum

Cusp (Figure 2-13). A cusp is a pointed or rounded
elevation of enamel found on cuspids and on the chewing surfaces
of bicuspids and molars. Cuspids have one cusp that represents
the tooth’s cutting edge. Maxillary bicuspids and the mandibular
first bicuspids have two cusps, one buccal and one lingual. The
mandibular second bicuspid normally has three cusps, one buccal
and two lingual. The lingual cusps are subdivided into a mesiolingual
and a distolingual.

Figure
2-13. Cusp

All maxillary molars have four cusps, two buccal and two lingual.
The two buccal cusps are subdivided into a mesiobuccal and a distobuccal.
The two lingual cusps are subdivided into a mesiolingual and a distolingual.
(Once in a while, the mesiolingual cusp of a maxillary first molar
carries an underdeveloped, rudimentary cusp called the cusp of
Carabelli.)

Themandibular first molar has five cusps, three buccal and
two lingual. From anterior to posterior, the three buccal cusps are
subdivided into a mesiobuccal, a distobuccal, and a distal. The two
lingual cusps are divided into a mesiolingual and a distolingual.

Themandibular second molarhas four cusps called the mesiobuccal,
distobuccal, mesiolingual, and distolingual.

Ridge. Any linear elevation found on the surface of a tooth.

Marginal Ridge
(Figure 2-14). A marginal ridge is a linear, rounded border of enamel
that forms the mesial and distal margins of anterior teeth as viewed
from the lingual, and the mesial and distal borders of occlusal surfaces
on posterior teeth.

Lingual Ridge
(Figure 2-15). The ridge of enamel that extends from the cingulum
to the cusp tip on the lingual surface of most cuspids is called
the lingual ridge.

Cusp Ridge
(Figure 2-16). Each cusp has four cusp ridges radiating from its
tip. They are named according to the direction they take away from
the cusp tip (for example, mesial, distal, facial, or lingual).

Figure 2-14. Marginal
Ridge

Figure 2.15.
Lingual Ridge

Triangular Ridge
(Figure 2-17). The occlusal surface of a cusp is composed of a mesial
and a distal incline. These two inclines meet to form a triangular
ridge of enamel that descends from the tip of the cusp to the central
portion of the occlusal surface. A triangular ridge is either a facial
or a lingual cusp ridge, depending on where the cusp is located. Cusps
are described in some mouths as being "pointy" and in others as being
"flat" or "blunt." Most "pointy" posterior teeth have high cusp angle
values (Figure 2-18). A cusp angle is the angle that a triangular ridge
makes with a plane perpendicular to the long axis of the tooth.

Figure 2-17. Triangular Ridge

Figure 2-18. Cusp Angle

Tr
ansverse Ridge (Figure 2-19). A transverse
ridge is the union of a buccal and lingual triangular
ridge that crosses the surface of a posterior tooth
transversely (roughly 90 degrees to both the buccal
and lingual tooth surfaces).

Oblique Ridge
(Figure 2-20). The only tooth on which an oblique
ridge is found is the maxillary molar. An oblique
ridge consists of a union between the triangular ridge
of the distobuccal cusp and the distal cusp ridge of
the mesiolingual cusp.

Cusp Inclines.
A cusp incline or inclined plane is
the sloping area found between two cusp ridges. To
name an incline, you must combine the names of the
cusp ridges that define a large part of its borders,
for example, the distolingual incline of the
buccal cusp of a maxillary first bicuspid (Figure 2-16).

•
Crown Concavities

Fossae

Lingual Fossa ( Figure 2-21). The lingual fossa is
an irregular, rounded concavity bound by the mesial
marginal ridge, distal marginal ridge, cingulum, and
incisal edge of the lingual surface of an incisor tooth.
Lingual fossae are also found on both sides of the lingual
ridge of a cuspid tooth.

Triangular Fossa
(Figure 2-22). Triangular
fossae are located adjacent to marginal ridges
on the occlusal surfaces of posterior teeth. There
are two kinds of triangular fossae, a mesial and a
distal.

Figure 2-19. Tranverse Ridge

Figure 2-20. Obligue Ridge

Figure 2-21. Lingual Fossa

Figure 2-22. Triangular Fossa

Central Fossa
(Figure 2-23). A central fossa is a centrally
located depression or concavity found on the occlusal
surface of molars and mandibular second bicuspids.
The other bicuspids have mesial and distal triangular
fossae, but do not have a central fossa.

Sulcus (Figure 2-24). A sulcus is an
elongated valley or depression in the surface of a
tooth formed by the inclines of adjacent cusps or
ridges. As an example, a central sulcus is a major
linear depression that traverses the occlusal surface
of a posterior tooth from mesial triangular fossa
to distal triangular fossa. Developmental grooves
are found in the bottoms of sulci.

Developmental
Groove (Figure 2-25). A developmental
groove is the junction line between the inclined
walls of a sulcus. Developmental grooves represent
lines of union between lobes of the crown during
its formation. These grooves appear on labial,
occlusal, buccal, and lingual surfaces, and are
least apparent on the labial aspect of anteriors.

Supplemental Groove (Figure 2-26). A minor, auxiliary
groove that branches off from a much more prominent
developmental groove. Supplemental grooves
do not represent the junction of primary tooth
parts.

Fissure (Figure 2-27). A linear fault that
sometimes occurs in a developmental groove. A fissure
represents a lack of union between the inclined
walls of a sulcus.

Pit
. A pit is a small, pinpoint fault on the
surface of a tooth; a pit is usually found at the
end of a developmental groove or at a place where two
fissures intersect.

Maxillary Molar

Mandibular Molar

Figure 2-23. Central Fossa

Figure 2-24. Sulcus

Figure 2-26. Supplemental Groove

Figure 2-25. Developmental Grooves

Figure 2-27. Fissure

Maxillary Central Incisor (Facial View)

1. Lobe

2. Developmental
Groove

3. Cemento–Enamel
Junction

4. Incisal Edge

Figure 2.28. Maxillary Central Incisor (Facial View)

Application.
Figures 2-28 through 2-33 show specific convexities and depressions
on anterior and posterior teeth. You should be able to name the coronal features
of teeth after you study these figures closely.

Figure 2-29. Maxillary Central Incisor (Lingual View)

1. Incisal Edge
5. Distal Marginal Ridge

2. Mesio-Inciso Angle
6. Lingual Fossa

3. Disto-Inciso Angle
7. Cingulum

4. Mesial Marginal Ridge
8. Cemento-Enamel Junction

Mandibular Cuspid (Lingual View)

1. Cusp Tip
5. Cingulum

2. Mesial Cusp Ridge
6. Mesial Marginal Ridge

3. Distal Cusp Ridge
7. Distal Marginal Ridge

4. Lingual Ridge

Figure 2-30. Mandibular
Cuspid (Lingual View)

Maxillary Second Bicuspid (Occlusal View)

1. Buccal Cusp

2. Lingual Cusp

3. Central Sulcus (Developmental Groove)

4. Supplemental Groove

5. Mesial Marginal Ridge

6. Distal Marginal Ridge

7. Mesial Triangular Fossa

8. Distal Triangular Fossa

9. Buccal Triangular Ridge (Crest)

10. Lingual Triangular Ridge (Mesial Incline)

11. Transverse Ridge

12. Mesial Cusp Ridge

13. Distal Cusp Ridge

Figure 2.31.Maxillary Second
Bicuspid (Occlusal View)

Maxillary First Molar
(Occlusal View)

1. Mesio-BuccalCusp

2. Disto-Buccal Cusp

3. Mesio-Lingual Cusp

4. Disto-Lingual Cusp

5. Buccal Developmental Groove

6. Lingual Developmental Groove

7. Central Sulcus (Developmental Groove)

8. Supplemental Groove

9. Mesial Marginal Ridge

10. Distal Marginal Ridge

11. Mesial Triangular Fossa

12. Distal Triangular Fossa

13. Central Fossa

14. Disto Buccal Triangular Ridge (Crest)

15. Oblique Ridge

16. Mesial CuspRidge

17. Distal Cusp Ridge

18. Cusp of Carabelli

Figure 2.32 Maxillary First Molar (Occlusal View)

Mandibular First Molar (Occlusal View)

1. Mesio-Buccal Cusp

2. Disto-Buccal Cusp

3. Distal Cusp

4. Mesio-Lingual Cusp

5. Disto-Lingual Cusp

6. Buccal (Developmental Groove)

7. Central Sulcus

8. Supplemental Groove

9. Mesial Marginal Ridge

10. Distal Marginal Ridge

11. Mesial Triangular Fossa

12. Distal Triangular Fossa

13. Central Fossa

14. Disto-Buccal Triangular Ridge (Distal Incline)

15. Disto-Lingual Triangular Ridge (Crest)

16. Tranverse Mesial

17. Mesial Cusp Ridge

18. Distal Cusp Ridge

Figure 2.33. Mandibular First Molar (Occlusal View)

Figure 2.34.
Contact Area

Round

Figure 2-35.
Embrasures

Rectangular

Trapezoid

Rhomboid

Figure 2.36. Occlusal Surface Outlines of Posterior Teeth

n
Proximal Surface Contact Characteristics

¨
Contact Points or Areas (Figure 2-34)

Teeth make contact with one
another at points or areas on the greatest contour of their proximal surfaces.
The places where adjacent teeth make point contact are called contact
points. Contact points become wider and flatter in time from wear that
occurs during functional movements (chewing) or parafunctional movements
(grinding). A flattened contact point is called a contact area.

¨ Embrasure(Figure 2-35)

An embrasure is a space diverging
from the contacting proximal surfaces of two adjacent teeth. There are
four of these spaces or embrasures recognized. They are the facial, lingual,
gingival, and occlusal or incisal (depends on whether they are posterior
or anterior teeth). The gingival embrasure is located cervical to
the contacting areas of adjacent teeth. A gingival embrasure has other
names like cervical embrasure, apical embrasure, interproximal
space, and septal space. Interdental palillae (gingival
tissue) fill interproximal spaces to a greater or lesser extent.

n
Occlusal Surface Outlines of Posterior Teeth (Figure 2-36)

¨
Circular Rounded in Outline

The occlusal surfaces of the
lower bicuspids are circular in outline.

¨
Rectangular

The occlusal surfaces of the
lower second molar and the upper bicuspids are often described as being
rectangular or oblong in outline.

¨ Trapezoid

A trapezoid is a plain
four-sided figure with two parallel sides. The occlusal surface of the lower
first molar is said to be trapezoidal in outline.

¨ Rhomboidal

A rhomboid is shaped
as an equilateral parallelogram having two opposing oblique angles. The occlusal
surfaces of the upper molars are rhomboidal in outline.

v
Descriptions of Individual Teeth

n
Overview

In the following
pages each tooth of the permanent dentition is described, except for the
third molars, which are not reproduced in artificial teeth. In each instance, the tooth from the right side of the mouth is illustrated. The
teeth are described as they usually look, but it should be mentioned that
teeth vary considerably from one person to another and that certain teeth
in the dentition tend to vary more than others. Included in the illustrations
of the bicuspids and the molars are drawings that show angles that can
be carved in reproducing the occlusal surfaces of these teeth. The broken
lines shown in the illustrations of the facial and lingual surfaces of
the teeth indicate proper food deflection contours.

The drawings in this section were adapted from those
appearing in the Ney Crown and Bridge Manual, J. M. Ney Co., Hartford, Conn.

n
Maxillary Central Incisor

The maxillary central incisor (Figure 2-37) is the tooth nearest the median line in the maxillary
arch.

¨ The facial surface is broad and resembles a thumbnail in
outline. The right maxillary central incisor may be distinguished from the
left maxillary central incisor because the distoincisal angle is more rounded
than the mesioincisal angle, and the incisal edge slopes slightly gingivally
in a mesiodistal direction. The facial surface is convex both mesiodistally
and incisocervically. Three distinct lobes may be seen in the incisal portion;
they are separated by two developmental grooves.

¨ The lingual surface appears slightly smaller than the facial
surface and the cervical portion is narrower. The large lingual fossa is
bounded by prominent mesial and distal marginal ridges. There is a cingulum
in the cervical portion, and there may be a pit in conjunction with the cingulum.

¨ Viewed on end, the incisal edge appears nearly straight.
Most of the wear is on the lingual portion of the edge, so the edge becomes
beveled lingually. The cingulum lies more to the distal side of the tooth
than to the mesial side.

¨ The mesial surface looks like a wedge. The apex of the wedge
is at the incisal edge of the tooth. The facial outline is slightly convex.
The lingual outline is slightly concave from the incisal edge to the cingulum
and convex from the cingulum to the cervical margin.

Figure 2-37. Maxillary Central Incisor

Figure 2-38. Maxillary Lateral Incisor

¨ The distal surface closely resembles the mesial surface.
The lingual outline is more concave in the incisal portion than it is on
the mesial surface.

n Maxillary Lateral Incisor

The maxillary
lateral incisor (Figure 2-38) is the second tooth from the median line
in the maxillary arch. It resembles the central incisor but is smaller
in all dimensions.

¨ The facial surface is narrower and shorter than that
of the central incisor. The distoincisal angle is more rounded than the
mesioincisal angle. The distal portion of the incisal ridge slopes upward
toward the distoincisal angle. The facial surface is convex.

¨ The lingual surface resembles the facial surface in
peripheral outline except that the cervical portion is narrower. The features
of this surface vary considerably from one individual to another. Proportionally,
the lingual surface characteristics of a lateral incisor are more marked
than similar features on a central incisor.

¨ Viewed on end, the incisal edge appears nearly straight.
The cingulum lies slightly to the distal side of the tooth.

¨ The mesial surface, like that of the central incisor,
is wedge-shaped. The apex of the wedge is at the incisal edge. The incisal
edge lies somewhat further lingually than it does in the central incisor.

¨ The distal surface resembles the mesial surface, but
the facial outline is more convex and the incisal portion of the lingual
outline is more concave.

n Maxillary Cuspid

The maxillary
cuspid (Figure 2-39) is the third tooth from the median line in the
maxillary arch. It is located at the corner of the arch, and its long root
is embedded in the canine (cuspid) eminence. The maxillary cuspid is usually
the longest tooth in either jaw. Since it resembles a dog’s tooth, it is
sometimes called the canine.

¨ The incisal portion of the facial surface is much broader
than the cervical portion. The mesial and distal cusp ridges of the incisal
edge slope downward toward the center to meet at the tip of the cusp. The
distal slope is longer than the mesial slope. The facial surface is convex.
It is divided into mesial and distal surfaces by the facial ridge. The
ridge extends from the tip of the cusp to the point of greatest convexity.
The mesiofacial surface of the cuspid falls on the curve of the arch formed
by the anterior teeth. The distofacial surface conforms to the buccal alignment
of posterior teeth.

Figure 2-39. Maxillary Cuspid

¨ The lingual surface resembles the facial
surface in outline, but the cervical portion is narrower. The mesial
and distal marginal ridges prominent, and a strong lingual ridge
runs from the tip of the cusp to the cingulum. The maxillary cuspid
has the largest cingulum of all the anterior teeth.

¨ Viewed
on end, the incisal edge is slightly curved. The lingual
portion of the tooth appears rugged, with the ridges and grooves
being very well defined.

¨ The
mesial surface is roughly triangular. From this aspect, the
cuspid appears much thicker than the incisors.

¨ The distal surface is shaped very much like the
mesial surface but is shorter because the distal portion of the
incisal edge slopes further cervically than the mesial portion.

n
Maxillary First Bicuspid

The maxillary first bicuspid (Figure 2-40)
is the fourth tooth from the median line in the maxillary arch.
It is the first posterior tooth. The bicuspids are sometimes called
premolars because they are just in front of the molars:

¨ The
facial surface resembles that of the cuspid in outline, but
it is shorter occlusocervically and not quite as convex. The slopes
of the mesial and distal cusp ridges are about equal in length.
The facial ridge is prominent.

¨ The
lingual surface is much smaller than the facial surface in
all dimensions but is generally similar in outline. The lingual
cusp is shorter than the facial cusp and is located mesial to the
midline of the tooth.

¨ The
occlusal surface is broader facially than lingually. There are
two cusps, the facial cusp and the lingual cusp. The mesial and distal
marginal ridges correspond to the marginal ridges of the anterior
teeth. The proximal surfaces converge toward the lingual; the distal surface
converging the most.

The mesial fossa is distal to the mesial marginal
ridge and the distal fossa is mesial to the distal marginal ridge.
The facial and lingual triangular ridges extend from the tips of
the cusps to the central groove. This groove ends at the mesial
and distal pits. The mesial and distal marginal grooves arise from
the mesial and distal pits and end on the mesial and distal surfaces,
respectively.

¨ The
mesial surface is roughly rectangular in outline. The facial
and lingual outlines are convex. The mesial surface is generally
convex except for a concave area on the facial portion of the surface
above the cervical margin. The mesial marginal groove extends onto
the mesial surface.

¨ The
distal surface resembles the mesial surface but does not have
the concave area above the cervical margin.

n
Maxillary Second Bicuspid

The maxillary second bicuspid is the fifth
tooth from the median line in the maxillary arch. It closely resembles
the first bicuspid but is more rounded in outline (Figure 2-41).

¨ The
lingual surface is only slightly shorter than the facial surface
because the facial and lingual cusps are nearly equal in length.
This surface is also slightly narrower than the facial surface.
The lingual surface is smoothly convex in all directions, and its
greatest convexity is in the cervical third.

¨ The
occlusal surface has, in general, the same form and features
as the occlusal surface of the first bicuspid. However, the facial and lingual
portions are more nearly equal in size and the mesial and distal
pits are closer together.

¨ The
mesial surface is wider in the cervical portion
than in the occlusal portion. The facial outline is slightly
convex, except in the central portion. The lingual outline is
convex. Both cusps appear more rounded that the cusps of the
first bicuspid.

¨ The
distal surface is slightly shorter than the
mesial surface; however, it is about the same width. The facial
and lingual outlines are convex. The surface is smoothly convex
except at the distal marginal groove.

n
Maxillary First Molar

The maxillary first molar (Figure 2-42) is the
sixth tooth from the median line in the maxillary arch. It is
the largest tooth in either arch. The maxillary and mandibular
first molars are often called 6-year molars:

¨ The
facial surface is roughly heart shaped in outline. The mesiofacial
and distofacial cusps form the occlusal border and the facial
groove divides the cusps. The surface is generally convex, except
at this groove. The surface has three ridges. A ridge extends
perpendicularly from the tip of each cusp and a third ridge extends
horizontally in the cervical portion.

¨ The mesiolingual
and distolingual cusps outline the occlusal border of the lingual
surface. The mesiolingual cusp is the largest of the posterior
teeth. Quite often this tooth has a fifth cusp, the cusp of Carabelli,
which is on the lingual surface of the mesiolingual cusp. This
cusp, when present, is shorter than the other cusps and does not
form part of the occlusal surface. The lingual surface is generally
convex, except at the distolingual groove.

Figure 2-40. Maxillary First Bicuspid

Figure 2-41. Maxillary Second Bicuspid

Figure 2.42. Maxillary First Molar

Figure 2.43. Maxillary Second Molar

¨ The
occlusal surface is roughly rhomboidal. The cusps are large
and prominent, with broad surfaces broken up into rugged ridges
and well-defined grooves. The mesiolingual cusp is the largest
of the cusps. The distolingual groove separates it from the distolingual
cusp. An oblique ridge connects the mesiolingual and distofacial
cusps. It runs parallel to the distolingual groove. The facial
groove runs from the central pit onto the facial surface. The mesial
and distal pits lie near the mesial and distal marginal ridges,
respectively.

¨ The
mesial marginal groove which starts at the mesial pit notches
the occlusal border of the mesial surface. A double convexity marks
the lingual margin if the cusp of Carabeli is present.

¨ The
distal marginal groove, which starts at the distal pit notches
the occlusal border of the distal surface.

n
Maxillary Second Molar

The maxillary second molar (Figure 2-43) is the
seventh tooth from the median line in the maxillary arch. It is
quite similar to the first molar; however, it is smaller. The tooth
is often called the 12-year molar:

¨ The
facial surface of the maxillary second molar is less symmetrical
than that of the first molar. The mesiofacial cusp is larger than
the distofacial cusp. The facial groove lies nearer to the distal
surface than it does to the mesial surface. The same three ridges
appear on the facial surface as appear on the facial surface of
the first molar.

¨ The occlusal border of the lingual
surface is marked by two cusps, the mesiolingual and the
distolingual. The mesiolingual cusp is the largest. (The
distolingual cusp is not fully reproduced in artificial teeth. For
this reason, many of these artificial teeth appear triangular when
viewed occlusally). The second molar has no cusp of Carabelli.
The cervical border is nearly straight. The lingual surface is
generally convex.

¨ The
occlusal surface is very similar to the occlusal
surface of the first molar.

¨ The
mesial surface is fairly symmetrical in outline.
The mesiofacial cusp is slightly longer than the mesiolingual
cusp. The facial outline is nearly straight, but the lingual
outline is distinctly convex.

¨ The
distal surface is somewhat smaller than the
mesial surface. The distofacial cusp is longer than the distolingual
cusp. The facial outline appears less convex than it does from
the mesial aspect.

n
Mandibular Central Incisor

The mandibular central incisor (Figure
2-44) is the first tooth from the median line in the mandibular
arch. It is the smallest tooth in either arch and the simplest
in form:

¨ The
facial surface is widest at the incisal edge. The mesioincisal
and distoincisal angles are close to being 90 degree angles. The
mesial and distal borders are almost parallel in the incisal portion;
in their middle and cervical portions the outlines converge but
do not meet. The facial surface is convex. There are three lobes, separated
by two developmental grooves. The grooves are more faint than they
are in the maxillary central incisor and often disappear entirely.

¨ The
lingual surface is quite similar in outline to the facial surface;
however, the cervical portion is more narrow. The incisal portion
of the lingual surface is concave. The cingulum, which begins fairly
close to the cervical margin, blends more smoothly with the rest
of the lingual surface than it does on the maxillary incisors.

¨ Viewed
on end, the incisal edge appears nearly straight. In an
adult, the edge is worn smooth and sharp.

¨ The
mesial surface is wedge-shaped. The facial outline is convex,
and the lingual outline is concave in the incisal and middle portions
and convex in the cervical portion. The mesial surface is almost
flat, incisogingivally.

¨ The
distal surface closely resembles the mesial surface.

n Mandibular
Lateral Incisor

The mandibular lateral incisor (Figure
2-45) is the second tooth from the median line in the mandibular
arch. Although it resembles the mandibular central incisor, it is
wider and longer:

¨ The facial surface is less symmetrical than
the facial surface of the mandibular central incisor. The incisal
edge slopes upward toward the mesioincisal angle, which is slightly
less than 90 degrees. The distoincisal angle is rounded. The mesial
border is more nearly straight than the distal border. The latter
is slightly convex in the incisal portion and slightly concave
in the middle and cervical portions. The facial surface is convex.

¨ The lingual surface is similar in outline
to the facial surface. The mesial and distal borders converge
more sharply than they do on the facial surface. The incisal
portion of the lingual surface is concave. The cingulum is quite
large but blends smoothly with the rest of the surface.

¨ Viewed
on end, the incisal edge forms a nearly straight line
that slants lingually toward its distal end. This is because
the distal portion of the facial surface is more convex than
the mesial portion.

¨ The
mesial surface is wedge-shaped. The facial outline is convex.
The lingual outline is concave in the incisal portion and convex
in the middle and cervical portions.

¨ The
distal surface is slightly shorter than the
mesial surface because the incisal edge slants downward toward
the distoincisal angle. The incisal portion of the distal surface
is thicker than the incisal portion of the mesial surface.

n
Mandibular Cuspid

The mandibular cuspid (Figure 2-46) is
the third tooth from the median line in the mandibular arch.
It is similar to the maxillary cuspid, but is narrower:

¨ The
facial surface is asymmetrical in outline. The
distal portion of the surface is shorter and broader than the
mesial portion, and consequently the distal cusp ridge of the
incisal edge is much longer than the mesial edge. The mesial
border is slightly convex. The upper portion of the distal border
is very convex, and the lower portion is slightly concave. The
three lobes are quite distinct cervically. The lingual ridge
divides the surface into two planes. The ridge blends smoothly
with the cingulum, which is small and confined to the cervical
portion of the tooth.

Figure 2.44. Mandibular Central Incisor

Figure 2-45. Mandibular Lateral Incisor

Figure 2-46. Madibular Cuspid

Figure 2-47. Mandibular First Bicuspid

¨ Viewed on end, the incisal edge
forms two curves that meet at the tip of the cusp. The mesial portion
of the facial outline is convex, but the distal portion is slightly flattened.
The mesial curve follows the alignment of the facial surfaces of the anterior
teeth. The distal part of the facial outline conforms to the buccal surface
alignment of posterior teeth. The cingulum appears uniformly curved on
both sides.

¨ The mesial surface more nearly resembles that of the
incisors than the mesial surface of the maxillary cuspid in outline. The
facial outline is convex. The lingual outline is chiefly concave except
near the cervical margin. The mesial surface is generally convex.

¨ The distal surface is shorter than the mesial surface
but is of about the same width. The incisal portion is very convex both
faciolingually and incisogingivally. The cervical portion is concave
incisogingivally.

n Mandibular First
Bicuspid

The mandibular
first bicuspid (Figure 2-47) is the fourth tooth from the median line
in the mandibular arch. It is the smallest and least typical of the bicuspids.

¨ The facial surface is shaped somewhat like a bell because
the cervical portion is markedly constricted in comparison with the occlusal
portion. The distal cusp ridge of the occlusal border is slightly longer
than the mesial cusp ridge, and the distoincisal angle is more rounded
than the mesioincisal angle. The distal portion of the surface is slightly
shorter and broader than the mesial surface. The surface is convex.

¨ The lingual surface is much smaller than the facial
surface because the lingual cusp is smaller than the facial cusp. The tip
of the lingual cusp is closer to the mesial margin than to the distal margin.
The surface is convex.

¨ The occlusal surface is marked by a strong facial cusp
and a lingual cusp that may appear almost rudimentary. The marginal ridges
are well defined. The strong lingual ridge of the facial cusp and the facial
ridge of the lingual cusp may join, forming a transverse ridge. In this
instance, the central groove would be very faint.

¨ The mesial surface is irregular in outline. From this
aspect the tooth appears to be tipped lingually. The facial cusp forms
most of the occlusal outline. The facial outline is very convex and the
greatest convexity is in the cervical third. The lingual outline is fairly
straight. Occlusocervically, the mesial surface is very convex in the occlusal
portion and concave in the cervical portion.

¨ The distal surface is similar to
the mesial surface.

n Mandibular Second Bicuspid

The mandibular
second bicuspid (Figure 2-48) is the fifth tooth from the median line
in the mandibular arch.

¨ The facial surface is very similar to the surface of
the mandibular first bicuspid. The facial ridge is prominent, and the surface
is convex.

¨ The lingual surface is similar to the surface of the
mandibular first bicuspid, with the exception that there may be two cusps,
the mesiolingual and the distolingual.

¨ The occlusal surface may appear in a number of forms.
In the form pictured, the mesial and distal triangular fossae are quite
distinct as they join the short central groove. There are three pits, the
central, the mesial, and the distal.

¨ The mesial surface is similar to the surface of the
mandibular first bicuspid, but it is more regular in outline. The surface
is convex faciolingually. Occlusocervically, the occlusal portion is convex,
and the cervical portion is concave.

¨ The distal surface is very similar to the mesial surface.

n Mandibular First Molar

The mandibular
first molar (Figure 2-49) is the sixth tooth from the median line in
the mandibular arch. It is also the largest tooth in the mandibular arch.
The maxillary and mandibular first molars are often called "6-year" molars.

¨ The facial surface presents three cusps: the mesiofacial,
the distofacial, and the distal. The mesiofacial cusp is the largest and
the distal is the smallest. The distofacial cusp, though smaller than the
mesiofacial cusp, may be slightly higher. The mesiofacial (facial) groove,
which may end in a pit, separates the mesiofacial and distofacial cusps.
The distofacial groove separates the distofacial and distal cusps. The
facial surface is convex except at the grooves.

¨ The lingual surface has a mesiolingual cusp and a distolingual
cusp, which are similar in outline. They are separated by the sharply defined
lingual groove. The surface is slightly convex.

¨ The occlusal surface of this tooth, unlike the surface of
the maxillary first molar, is formed by all five cusps and is trapezoidal
in shape. There are three pits, the mesial,

the central, and the distal. A central groove,
which connects these pits, divides the occlusal surface into the
lingual and facial halves. From the occlusal aspect, the mesiofacial
cusp appears the largest and the distal cusp appears the smallest.

¨ The
mesial surface is wider in the cervical portion than it is
in the occlusal portion because the occlusal and middle thirds
of the facial outline slope outward occlusocervically. The lingual
outline is quite straight and nearly perpendicular.

¨ The
distal surface is more symmetrical than the mesial surface
because the facial outline is more nearly perpendicular than it
is on the mesial surface.

n
Mandibular Second Molar

The mandibular second molar (Figure 2-50)
is the seventh tooth from the median line in the mandibular arch.
It is one of the 12-years molars.

¨ The
facial surface is almost symmetrical in outline, and the mesiofacial
and distofacial cusps appear nearly equal in size. The two cusps
are separated by the deep facial groove. There is no third cusp,
as on the mandibular first molar.

¨ The
lingual surface is symmetrical, but the mesiolingual cusp is
slightly longer and bulkier than the distolingual cusp. The lingual
groove is shorter and less distinct than the groove on the facial
surface.

¨ The occlusal surface is rectangular
in shape. From this view the mesiofacial cusp appears slightly larger than
the three other cusps. The occlusal surface has three pits, the mesial,
the central, and the distal.

¨ The mesial surface resembles the mesial surface of the
mandibular first molar; however, it is shorter. The facial outline is convex
occlusocervically. The occlusal portion of the lingual outline is convex
and the cervical portion is more nearly straight.

¨ The distal surface resembles the mesial surface.

Anatomy of Facial and Oral Structures

Below is a table
showing the sequence of eruption of the primary dentition:

Below is a table
showing the sequence of eruption of the permanent set:

Note: *b stands for buccal or toward the cheek;lstands for lingual or towards the tongue or palate.